This invention relates to a sorter which causes a plurality of vertically spaced air, art bins to shift upward and downward to sort sheets out.
In recent years, in an image forming apparatus such as a copying machine and a printer for transferring the same document image to a plurality of copy sheets, there has been widely used a sorter for sorting these copy sheets out to a plurality of bins automatically. Particularly, there has been recently used a sorter provided with a function of applying a specified mechanical sheet processing to the sorted sheets on the bins by means of a stapler and a punch. Since the conventional sorter of this type is constructed such that the stapler or the like moves close to or away from the bin so as to apply the processing to the sheet, the stapling is applied only to a specified corner portion of the sheet.
Recently, there has been an increasing demand for a sorter capable of applying a plurality of types of sheet processing including the stapling and punching to a desired position in a widthwise direction of the sheet. The following can be considered as one type of this sorter. Specifically, the sorter is provided with a support moving mechanism for moving a single support having a sheet processor such as a stapler and a punch arranged side by side thereon in the widthwise direction of the bin, and a bin moving mechanism for moving the bin toward the sheet processor so as to apply the sheet processing to the sheets placed on the bin. The sheets placed on the bin having moved toward the bin are pressed by a sheet holder, and a rear end portion of the bin is opened up. Thereafter, the support is moved to a desired position to apply a specified processing to the sheets.
In the sorter thus constructed, the bins are shiftable upward and downward to a position where the bin moving mechanism is provided. Accordingly, a home position of a stack of bins must be detected accurately in order to move the bins reliably to the position where the bin moving mechanism is provided. Further, upper and lower limits of vertically movable range must be detected accurately in order to prevent a failure from occurring due to the fact that the bins are shifted beyond the upper and lower limits of the range. The sorter in which the bin is moved toward the sheet processor, the sheets are held, and the rear end portion of the bin is opened up in this order requires a relatively large time until the sheet processing is completed.